Apparatus for introducing air to burners of reversing type furnaces



. HARTNE RODUCING A Nov. 24, 1953 J. Y 2,660,419

- APPARATUS FOR IR TO BURNERS OF REVERSING TYPE FURNACES 3 Sheets$heet 1Filed March 9, 1950 J. L. HARTNEY R INTRODUCING AIR TO BURNERS Nov. 24,1953 APPARATUS FO OF REVERSING TYPE FURNACES 3 Sheets-Sheet 2 FiledMarch 9, 1950 FIG. 2..

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APPARATUS FOR INTROD INC AIR TO BURNERS OF REVERSING TYPE FURNACES'Filed March 9, 1950 V 3 Sheets-Sheet 3 Ala -470//7e r/.

Patented Nov. 24, 1953 BURNERS NACES OF REVERSING TYPE FUR- James L.Hartney, Chicago, 111., assignor to United States Steel Corporation, acorporation of New Jersey Application March 9, 1950, Serial No. 148,619

7 Claims. (01. 263-45 This invention relates to improved, apparatus forintroducing air to the :burners of reversing type furnaces.

An object of the invention is to provide improved apparatus forpre-heating compressed air and selectively directing such air to eitherburner or set of burners in a reversing type furnace.

A further object of the invention is to provide improved systems fordirecting flow of compressed air from a heating device to either burneror set of burners in a reversing type furnace and automaticallymaintaining continuous flow of such fluid through the heating deviceduring changeovers and thereby preventing overheating of the heatingdevice.

A further object of the invention is to provide improved apparatusutilizing pre-heated compressed air as atomizing fluid for liquid fuelin open hearth furnace burners, thereby enhancing furnace efficiencyover that obtained with steam as atomizing fluid.

In accomplishing these and other objects of the invention, I haveprovided improved details of structure, a preferred form of which Yshown in the accompanying drawings, in which:

Figure 1 is a schematic view of a reversing type furnace equipped withan improved apparatus for introducing pre-heated air to the burnersembodying features of the present invention;

Figure 2 is a top plan View with parts broken away of a preferredconstruction of heat exchanger used in the apparatus shown in Figure 1;

Figures 3 and 4 are vertical sectional views of the heat exchanger takenrespectively on lines III-III and IV-IV of Figure 2;

Figure 5 is an enlarged vertical sectional view of the heat exchangershowing the wall construction;

Figure 6 is a side elevational view with parts broken away of apreferred construction of a multiple diaphragm by-pass valve used in theapparatus shown in Figure 1; and

Figure 7 is an exploded sectional view of the operating mechanism of thevalve shown in Figure 6.

Referring more in detail to the drawings:

In Figure 1 there is shown schematically a reversing type furnace I0,which can be for example an open hearth for manufacturing steel andwhich has two selectively operable burners I2 and I3 at opposite ends.The furnace is reversed periodically and thus is fired alternately fromthese two burners, as known in the art. There is shown at 14 an aircompressor which directs compressed air through a line [5 to a receivingtank I6. From the tank the air passes via a line 11 into a heatexchanger [8, where the air is heated to a fairly high temperature whichis maintained constant or nearly so, Line I! preferably has a pressureregulator l9 and a by-pass valve 20 for said regulator. The furnace,burners, air compressor, receiving tank, and pressure regulator may beof any standard construction; hence no more detailed'description isdeemed necessary. The preferred construction of heat exchanger isdescribed more fully hereinafter.

One purpose for which air can be introduced to the burners is as fuelatomizing fluid. In this instance the air is heated to a temperaturepreferably between 600 and 800 F, commonly being maintained at 700 F.The pressure commonly is maintained between and pounds per square inch,although none of these values are necessarily critical, as long as theyare maintained constant or nearly so.

Aline 2| extends from the heat exchanger and branches into lines 22 and23 which extend respectively to burners l2 and I3. These lines con tainnormally closed, pneumatically operated diaphragm type valves 24 and 25respectively for controlling flow of air to the burners. Inasmuch asthese valves may be of any standard construction and per se are not partof the present invention, no more detailed description is deemednecessary, When the furnace is fired from either burner, the appropriatevalve is opened and directs air to that burner,

The apparatus comprises a by-pass line 26 which discharges from pipe 2|into the atmosphere and which contains a valve 21. This valve is of thenormally open, pneumatically operated double diaphragm type and is morefully described hereinafter. The, apparatus comprises valve operatingmechanism which automatically opens valve 2'! unless either valve 24 or25 is open, in which case it automatically closes valve 21. Thus the aircontinues to circulate through the heat exchanger when valves 24 and 25are both closed as during changeovers in firing the furnace fromone setof burners to the other, as is done periodically in operation of thefurnace. Such circulation is needed to prevent overheating of the heatexchanger, since the temperature of air emerging from the heat exchangercan be fairly close to the maximum temperature which the heat exchangercan withstand. Also if the heat exchanger is overheated, there issubsequent difficulty in adjusting the air temperature to the desiredconstant.

The valve operating mechanism includes a control air line 28 which isconnected with line I! and thus receives compressed air from tank It.Line 28 preferably contains a filter 2 9 and a pressure reducing valve30, which both may be of any standard construction. Line 28 extends to afour-way control valve 3|, to whichare also connected an exhaust line 32and two lines 33 and 3.4 that extend to. valves 24 and 25 respectivelyfor operating these valves. Valve 31 has settings tov connect line 28with either line 3301' 34 and at the same time connect the other ofthese lines with exhaust line 32. Inasmuch as valves having suchsettings are known and per se are not part of the present invention, nomore detailed description is deemed necessary. Whenever the controlvalve admits air to line 33 or 34, valve 24 or 25 opens and air flowsthrough that valve from the heat exchanger to one of the burners.

Air lines and 35 extend from air lines 33 and 34 respectively to theby-pass valve 21. Whenever control valve 3| is actuated to relieve thepressure on the diaphragm of either of the normally closed valves 24 or25 and thus close this valve, it also relieves the pressure thatmaintains the normally open by-pass valve closed. The by-pass valvethereupon opens and maintains air circulation through the heat exchangervia by-pass line 26 and thus prevents overheating of the heat exchanger.The by-pass valve remains open until pressure is applied to thediaphragm of the other valve 24 or 25 to open this valve. At the sametime pressure is applied automatically to the by-pass valve via line 35or 36 and thus this valve closes, and circulation is resumed to one ofthe burners.

A preferred construction of heat exchanger 18 is shown in detail inFigures 2 to 5. The heat exchanger comprises an enclosure whose wallsare formed of a heat insulation lining 31 supported by longitudinallyextending channel-shaped casing members 38. Pairs of end plates 39 areinterposed between successive tiers of insulating material and casings(Figure 5). A spacer 48 and a horizontal bafiie 4| are interposedbetween each pair of end plates 39. The baffles are sup portedcantilever fashion from the end plates and thus are free to expand andcontract. The baffles extend alternately from opposite sides into theinterior of the heat exchanger as best shown in Figure 3 and define asinuous course for circulating waste products of combustion from thefurnace from which the heat is derived.

A fan 42 draws a portion of the products of combustion from furnace l0into the lower portion of heat exchanger 18 through an inlet 43. Theseproducts of combustion pass through the heat exchanger in the coursedefined by bailles 4| and are expelled at the top through an outlet 4tinto a stack 45 (Figure 1). The portion of such products which passthrough the heat exchanger is governed by a damper 43 preferably locatedin outlet 44.

The compressed air is maintained at a substantially constanttemperature, which may be controlled by regulating damper 46. Line 21contains a temperature indicating device 41 and line ll contains a flowindicating device 48. Damper 46 is regulated in accordance with readingson these indicating devices to maintain a flow of products of combustionthrough the heat exchanger sufiicient to heat the air to just thedesired temperature. Although the damper may be regulated manually, theaparatus preferably includes metering controls, connected to thetemperature and flow indicating devices 41 and 48 but not shown, forregulating the damper automatically. Inasmuch as such controls are knownand do not per se form a part of the present invention, no more detaileddescription is deemed necessary.

The heat exchanger has a pair of manifolds 49 and 50, each of which isdivided by partitions 5| and into a plurality of superposed compartments(Figure 4). The compartments on opposite manifolds are connected byU-shaped tubes 52, which extend between baffles 41 into the path ofcirculation of the products of combustion. Unheated compressed air isintroduced from line I! to the top chamber of manifold 49, whence itpasses through tubes 52 to the top chamber of manifold 50. Such air thenreturns to the second chamber of manifold 43 via the next set of tubes52. Air circulation betwen the manifolds continues through the entireheight of the manifolds and the heated air finally discharges from thebottom chamber of manifold 49 into line 2i, from which it may bedirected to either set of burners as already explained.

Figures 6 and 7 show a preferred construction of by-pass valve 21. Saidvalve includes the usual body, stem and closures, which are not shown indetail, since they may be of any standard construction. The operatingmechanism for this valve includes a pair of superposed flexiblediaphragms 53 and 54 housed within the usual pressure chamber 55. Aspring 56 normally urges the diaphragms to a retracted position againstthe back wall of the chamber and normally maintains the valve open. Airmay be admitted to the space behind diaphragm 53 to close the valve, orair may be admitted to the space between the two diaphragms also toclose the valve. The first of these spaces is connected to line 36 by aconnection 51 in the back wall of the chamber. The second of thesespaces is connected to line 35 by a connection 58 situated in a spacerring between the two diaphragms. The first space preferably has fillers60 and the second fillers 6| to separate the diaphragms slightly fromthe end wall and from each other when either is retracted. Thus it isseen that the by-pass valve is closed whenever air is admitted behindeither diaphragm on closing of either valve 24 or 25.

While the valve just described is particularly uited to use in thepresent instalaltion, similarly constructed valevs may be employed inother installations where it is desired to operate a valve from any oneof a multiple of sources. Such valves may be either of the normally opentype, as illustrated, or of the normally closed type.

From the foregoing description, it is seen that I have provided aneflicient apparatus for introducing pre-heated compressed air to eitherburner or set of burners in a reversing type furnace. The air iscontinuously heated by heat derived from waste products of combustionand circulation of air is automatically maintained at all timesincluding during changeover periods. Thus I have provided a system inwhich there is no likelihood of parts being overheated by failure tomaintain air circulation.

The present application is a continuation-inpart of my copendingapplication Serial No. 47,034, filed August 31, 1948, now Patent No.2,587,153, issued February 26, 1952. The double diaphragm valve formsthe subject matter of application Serial No. 160,067, filed May 4, 1950,which is a division of aforesaid application Serial No. 47,034. Themethod forms subject matter of application Serial No. 357,739, filed May2'7, 1353, which is a division of the present application.

While I have shown and described only a single embodiment of theinvention, it is apparent that modifications may arise. Therefore, I donot wish to be limited to the disclosure set forth but only by the scopeof the appended claims,

I claim:

1. In a reversible furnace having a pair of selectively operable burnersfor firing the furnace, an apparatus for supplying pre-heated compressedair to said burners comprising a source flow of air through said heatingdevice during changeovers in firing the furnace from one of said burnersto the other.

2. In a reversible furnace having a pair of selectively operable burnersfor firing the furnace, an apparatus for supplying pre-heated compressedair to said burners comprising a source of compressed air, a heatexchanger for preheating the air, a line for directing Waste products ofcombustion from the furnace through said heat exchanger for heating thelatter, lines for directing air from said heat exchanger selectively tosaid burners, valves in said lines for controlling fiow of airtherethrough, a by-pass from said heat exchanger discharging into theatmosphere, a valve in said lay-pass, and a pneumatic operatingmechanism connected to the valves in said lines and the valve in saidby-pass automatically opening the valve in said by-pass unless the valvein one of said lines is open, thereby automatically maintaining flow ofair through said heat exchanger during changeovers in' firing thefurnace from one of said burners to the other.

3. In a reversible furnace having a pair of selectively operable burnersadjacent opposite ends through which the furnace is fired alternately,an apparatus for supplying pre-heated compressed air to said burnerscomprising a source of compressed air, a heat exchanger, means fordirecting a portion of the products of combustion from the furnacethrough said heat exchanger, means for directing compressed air fromsaid source to said heat exchanger, lines for directing air from saidheat exchanger selectively to said burners, normally closedpneumatically operated valves in said lines for controlling flow of airtherethrough, a by-pass for air from said heat exchanger discharginginto the atmosphere, a normally open pneumatically operated valve insaid by-pass, and an operating mechanism for simultaneously opening oneof said normally closed valves and closing said normally open valve.

4. In a reversible furnace having a pair of selectively operable burnersadjacent opposite ends through which the furnace is fired alternately,an apparatus for supplying pre-heated compressed air to said burnerscomprising a source of compressed air, a heating device for pre-heatingair from said source, lines for directing air from said heating deviceselectively to said burners, normally closed pneumatically operateddiaphragm type valves in said lines for controlling flow of airtherethrough, a by-pass for air from said heating device discharginginto the atmosphere, a normally open pneumatically operated doublediaphragm type valve in said by-pass, and a pneumatic operatingmechanism for applying pressure behind the diaphragms of said valves foropening the normally closed valves and closing the normally open valve,said operating mechanism automatically releasing or applying pressure tothe valve in said Icy-pass on release or application of pressure to thevalve in either of said lines, thereby maintaining flow of air throughsaid heating device during changeovers in firing the furnace from oneburner to the other.

5. In a reversible furnace having a pair of selectively operable burnersadjacent opposite ends through which the furnace is fired alternately,an apparatus for supplying pre-heated compressed air to said burnerscomprising a source of compressed air, a heating device for pre-heatingair from said source, lines for directing air from said heating deviceselectively to said burners, normally closed pneumatically operateddiaphragm type valves in said lines for controlling fiow of airtherethrough, a by-pass for air from said heating device discharginginto the atmosphere, a normally open pneumatically operated doublediaphragm type valve in said by-pass, a control valve, a line connectingsaid control valve with said source of compressed air, an exhaust fromsaid controlvalve, and lines connecting said control valve with each ofsaid pneumatically operated valves for applying pressure to thediaphragms thereof and opening the normally closed valves and closingthe normally open valve, said control valve automatically releasing orapplying pressure to the valve in said by-pass on application or releaseof pressure to the valve in either of said first named lines, therebymaintaining flow of air through said heating device during changeoversin firing the furnace from one burner to the other.

6. In an apparatus for supplying compressed air to burners of areversible furnace, a device for pre-heating the air, a controlconnected to said pre-heating device for directing air to either set ofburners in the furnace, a by-pass for discharging air from thepre-heating device into the atmosphere, and a valve in said by-pass,said valve having a pressure chamber, a pair of diaphragms in saidpressure chamber, means connected to said control for admitting airbehind either of said diaphragms for operating the valve, and meansnormally retracting both of said diaphragms.

7. In an apparatus for supplying compressed air to burners of areversible furnace, a device for pre-heating the air, a controlconnected to said pre-heating device for directing air to either set ofburners in the furnace, a by-pass for discharging air from thepre-heating device into the atmosphere, and a normally open valve insaid by-pass, said valve having a pressure chamber, a pair of superposeddiaphragms in said pressure chamber, means connected to said control foradmitting air behind either of said diaphragms for closing the valve,and a spring normally retracting said diaphragms.

JAMES L. HAR'I'NEY.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,414,451 Arthur May 2, 1922 1,907,140 Bartholomew May 2, 19332,066,103 Fiorelli Dec. 29, 1936 2,090,771 Whitcomb Aug. 24, 19372,171,597 Parker Sept. 5, 1939 2,183,596 Trinks Dec. 19, 1939 FOREIGNPATENTS Number Country Date 903,404 France 'Jan. 15, 1945

